KENNEDY SPACE CENTER, FLA. - Workers on the mobile service tower on Launch Pad 17-B, Cape Canaveral Air Force Station, watch as the Space Infrared Telescope Facility (SIRTF) clears the platform. SIRTF will be attached to the Delta II rocket and encapsulated in its fairing before launch. Consisting of three cryogenically cooled science instruments and an 0.85-meter telescope, SIRTF is one of NASA?s largest infrared telescopes to be launched. It is the fourth and final element in NASA?s family of orbiting ?Great Observatories.? SIRTF will obtain images and spectra by detecting the infrared energy, or heat, radiated by objects in space. Most of this infrared radiation is blocked by the Earth's atmosphere and cannot be observed from the ground.